Changing trends in indigenous inequalities in mortality: lessons from New Zealand

We describe trends from 1951 to 2006 in inequalities in mortality between the indigenous (Māori) and non-indigenous (non-Māori, mainly European-descended) populations of New Zealand. We relate these trends to the historical context in which they occurred, including major structural adjustment of the economy from the mid 1980s to the mid 1990s, followed by a retreat from neoliberal social and economic policies from the late 1990s onwards. This was accompanied by economic recovery and the introduction of health reforms, including a reorientation of the health system towards primary health care.

Abridged period lifetables for Māori and non-Māori from 1951 to 2006 were constructed using standard demographic methods. Absolute [standardized rate difference (SRD)] and relative [standardized rate ratio (SRR)] mortality inequalities for Māori compared with European/Other ethnic groups (aged 1-74 years) were measured using the New Zealand Census-Mortality Study (an ongoing data linkage study that links mortality to census records) from 1981-84 to 2001-04. The SRDs were decomposed into their contributions from major causes of death. Poisson regression modelling was used to estimate the extent of socio-economic mediation of the ethnic mortality inequality over time.

Life expectancy gaps and relative inequalities in mortality rates (aged 1-74 years) widened and then narrowed again, in tandem with the trends in social inequalities (allowing for a short lag). Among females, the contribution of cardiovascular disease to absolute mortality inequalities steadily decreased, but was partly offset by an increasing contribution from cancer. Among males, the contribution of CVD increased from the early 1980s to the 1990s, then decreased again. The extent of socio-economic mediation of the ethnic mortality inequality peaked in 1991-94, again more notably among males.

Our results are consistent with a causal association between changing economic inequalities and changing health inequalities between ethnic groups. However, causality cannot be established from a historical analysis alone. Three lessons nevertheless emerge from the New Zealand experience: the lag between changes in ethnic social inequality and ethnic health inequality may be short (<5 years); both changes in the distribution of the social determinants of health and an appropriate health system response may be required to address ethnic health inequalities; and timely monitoring of ethnic health inequalities, based on high-quality ethnicity data, may help to sustain political commitment to pro-equity health and social policies.